Electric furnace of the resistor type



Nov. 4 1924.

1,513,890 H. BRYAN ET Al.

ELECTRIC FURNACE OF THE RESISTOR TYPE Filed Oct. 24, 192.3

*.'IIII IJIIII/IIIII,

i l s s Patented Nov.` 4, 1.924.

*UNITED STATES PATENT OFFICE.`

HARRY BRYAN, ABNON' L. MEHRING,.AND WILL'IAHH. ROSS, OF WASHINGTON, DIS-TBICT OF COLUMBIA, DEDICATED, BY HEHE ASSIGNMENTS, TO THE CITIZENS F THEUN'ITEDSTATES OfF AmIGA.

EEGTRG FURNACE OF THE BESISTOR TYPE.

Application Bled October 24, 1923. Serial No. 370,546.

(FILED UNDER THE AGT- 0F MARGH 3, 'l883, 22 STAT. L., 625.)

To allwhmnz'tmyconcem:

Be it known that we, HARRY BRYAN, ARNON L. MEHRING, and WILLIAM H. Ross,citizens of the United States of America, i and employees of theDepartment of riculture of the United States of Amerlca, residing atWashington, D. C., have invented certain new` and useful Improvements inElectric Furnaces of the Resistor Type; and We do hereby declare thefol.-

lowing to be a full, clear, and exact descrip-v tion of the invention,such as will enable others skilled in the art to'which it pertains tomake and'use the same.

This application is made under the act of Marche, 1883, 'chapter 143 (22Stat., 625) and the vinvention herein described and claimed maybe usedby the Government of the United States 'or any of its. oiiicers oremployees in the prosecution of Work for the Government and any personin the United States without the payment to us of any Vroyalty thereon.

This invention relates to an 'electric furnace of the resistor-type andhas for its ob- .ject to provide a furnace which is ca able of readytemperature control and o developing a higher temperature than ispossible to maintain in furnaces of. the muflie type with alloyresistance elements..

A further object of the invention is to provide a furnace which can bequickly charged or recharged and which admits of having the resistorelement easily replaced as desired. y

A still further object of the invention is to provide a means for thecollection of any gases or fumes which may be evolved from the charge inthe furnace'during its operation.-

With the foregoing and other objects in view this invention consists insuch novel features of construction, combination and arrangement lofparts as will be hereinafter more fully described and lillustrated inthe accompanying drawings and claims.

In describing the nvention'in detail reference will be had to theaccompanying drawings wherein like characters desi ate like andcorresponding parts throughout the several views and in which:

Fig'. 1 is a side elevation of furnace.

the improved clamps for connecting the circuit leads with the terminalsof the resistor.

Fig. 6 is a vertical cross section of the furnace taken ori the line 6-6of Fig. 3.

Fig. 7 is a horizontal cross section of one of the terminals of theresistor taken at the line 7 7 of Fig. 2.

Referring more particularly to the drawings, 1 designates the exteriorcasing of the furnace which is preferably cylindrical in shape andconstructed of such material as it inch sheet iron. The casing isflanged atthe front face to make a gasTtight joint with the sheet ironplate 2 which serves as asA the front end of the furnace.' The latter isinsulated from the furnace casing by means of asbestos vpacking 3 andfibre bushings 4 which surround the connecting bolts 5. The flanged headand rear face of the furnace casing serve to support the waterresistor8. -Terminal 6 as represented in Fig. 7 is machined from a cylinder ofbrass or similar material and is provided -with a water-inlet 9and'outlet 10. It is also provided with a flanged head 11 which can bescrewed into the terminal to make a gastight connection. The flangedhead is in -turn provided with a gas inlet 12 and a replaceable window13 which enables the charge in the furnace to be in plain view of `theoperator and through which readings may be made with an opticalpyrometer of the'temperature within the furnace... Terminal 7 is of thesame construction' as terminal 6 excepting that the anged head withwhich it is provided carries a gas 4outlet 14 and the use of a window isunnecessary. Each terminal is also provided with a' threaded graphitebushing 15 with which it makes close contact as represented in Eig. 7,and which is constructed of the same'materia] as the resistor. The boreof each bushing is of proper diameter to make good A cooled terminals6`and 7 of the graphite 19 and carborundum 20. A carbon cylin` der 21serves as a partition to protect the graphite resistor from theinsulating material.

In the operation of the furnace water is first allowed to flow throughthe terminals and the air in the furnace evacuated by means of anyordinary type' of exhaust' pump. The furnace is then filled with anon-oxidizing gassuch as nitrogen or carl:bon monoxide and the electriccurrent finally applied through the circuit leads 17 and 18. Variationsof temperature within' the furnace are most conveniently controlled inthe ordinary way by means of a transformer and switch board which varecapable of giving a suitable range of voltage in one volt steps. Thesliding contacts between the resistor and graphite bushings take up anyexpansion or contraction of the casing due to differences of temperaturein the furnace without impart-ing any appreciable strain on theresistor.

The addition of'a charge to the furnace or its withdrawal may be quicklymade by unscrewing the anged head of either terminal; In the same 'wayby removing the anged head 'from both terminals va worn out resistor maybe easily and quickly removed and a new one inserted in its place. Anyfume or other volatile material which is evolved in the operation of thefurnace may be easily' collected through the outlet of the rearterminal.

We are aware that the Arsem furnace as now'placed on the market is alsoa furnace of the graphite resistor type, but the resistor in thisfurnace is constructed in the form` of a helix and beingvery fragile is'necessarily suspended vertically. The opening and closing of thisfurnace as well as the replacement4 of the helix takes amuch longer timethan that required for the furnace embodied in this invention. TheArsemfurnace moreover operates under a high vvacuum and the recovery ofcorrosive fumes. such as those evolved in the experimental study of thevolatilization .of phosphoric acid from phosphate rock is impractical.

While the use of a resistor of the helix'v type is much more `fragileand expensive than the cylindrical form,. and the use of the latter is,therefore, to be preferred it is nevertheless possible when desired tosubstitu'te the helix type of resistor in our invention withoutotherwise modifying the form of the apparatus.

It will be understood that the invention is not limited to the specificembodiment shown and that various deviations may be made therefromWithout departing from the 'spirit and scope of the appended claims.

What we claim is: W 4 1. An electric furnace comprising a cylindricalgraphite resistor supported by` graphite bushings which make slidingcon` minals.

HARRY BRYAN. ARN ON L. MEHRING. WILLIAM H. ROSS. I'

Itact with said resistor, water-cooled cylin-

